Abstract: The valve structure of the present invention can completely eliminate the dead volume of a valve in closed position, thereby enhancing the precision and reliability of measurement. A valve chamber (3) is divided into an upper portion and a lower portion by a diaphragm (6). The whole circumference of the diaphragm (6) is fixed on the same level as the bottom of the valve chamber (3). A fluid inlet port (4a) is formed on the substantial center of the bottom face of the valve chamber (3). A stepped hole (7) is arranged concentrically with the fluid inlet port (4a) open to the valve chamber (3). A valve seat (8) composed of perfluoro-elastomer has a stepped element (8a) which corresponds to and is fitted in the stepped hole (7). A valve disc (10) projected through the bottom face of the diaphragm (6) is pressed against a ring projection (8b) of the valve seat (8) protruded into the valve chamber (3).

Abstract: Needle valves which are seated in valve seats defined by circular edges have DELRIN.RTM. tips for the purpose of minimizing unseating torque which would otherwise be excessive due to the thermal expansion and contraction characteristics of the valve seats and the needle valves. In salt spreaders with aluminum valve seats and steel needle valves, the needle valves become stuck in the valve seats if the needle valves are seated after operation in frigid weather and the salt spreaders are subsequently garaged to raise the temperature of the valve seat and needle valves. By utilizing the DELRIN.RTM. tips, the needle valves do not become stuck.

Abstract: A valve/actuator combination to operate off of low pneumatic pressures for use on tanker railcars including a valve having a valve body with a tank end, a valve seat near the tank end of the valve body, the valve seat having a valve sealing surface; a stem chamber extending through the valve body, the stem chamber having an actuator port, a seat port, and an outlet port; a valve stem slidably positioned in the stem chamber, the valve stem having a plug end and a plug attached to the plug end, the plug having a plug sealing surface to sealingly contact the valve sealing surface; an actuator having a hollow housing with a valve end, the valve end attached to the valve body; a plurality of piston assemblies, each having a piston slidable in the housing and a partition fixed in the housing, the piston and the partition defining an actuator chamber; piston spacers joining the pistons so that each piston is fixed in position with respect to the others; the pistons being operatively joined to the valve stem; a helic

Abstract: A fluid control valve operable in erosive fluid conditions includes a primary soft seat protected by a secondary hard seat. Two dead band areas control the fluid flow on valve opening and closing to spacially separate the soft seat from the flow stream. A diverter is provided to deflect the flow stream away from the soft seat.

Abstract: A valve plate in the form of a sheet metal preform is disclosed for a thermostatic valve. The preform includes an edge with a surrounding ring groove accommodating a rectangular cross section sealing ring. An exterior wall defining the ring groove is bent inward penetrating into the sealing ring to securely hold it in place.

Abstract: A valve stem seal for use in an internal combustion engine. The valve stem seal includes a leak resistant plastic seal member located at the bottom of a valve guide. The valve stem seal is secured in place around the bottom of the valve guide by a metallic outer case having a cylindrical shape. The valve stem seal is in continuous engagement with a reciprocating valve stem on the bottom portion of the valve guide system.

Abstract: A resilient seal for a liquid-gas accumulator of the type having a housing with a top gas port and a bottom liquid port. A valve assembly including a spring-loaded normally open poppet valve surrounded by a sleeve is positioned in the liquid port, and a device for controlling the opening and closing of the valve in response to the level of liquid in the housing is also provided within the housing. The resilient seal is positioned on top of the popper valve and comprises a first resilient seal member and a second resilient seal member. The first resilient seal member is positioned to seat on the first end of the sleeve outside of the valve seat as the valve closes thereby providing a secondary seal.

Abstract: A safety relief valve (12) for a pressure vessel (10) in which the main valve member (28) includes a valve plate or disc (52) and a retainer plate (64) having a flexible membrane or diaphragm (62) stretched therebetween in a taut relation to provide a frusto-conical shape (FIG. 3) for obtaining bubble-tight sealing against valve seat (26). A fluid chamber (116) is provided between valve plate (52) and retainer plate (64) and inlet fluid pressure is communicated through opening (118) of jack screw (106) to the fluid chamber (116) for providing inlet fluid pressure thereto to force valve plate (52) and retainer plate (64) apart for tensioning of flexible membrane (62) into a frusto-conical shape. A jack screw (106) is threaded within a bushing (94) carried by retainer plate (64). Upon rotation of jack screw (106), valve plate (52) and retainer plate (64) are forced away from each other for tensioning flexible membrane (62) into a frusto-conical shape.

Abstract: In a preferred embodiment, in a fluid flow valve having a body and having a movable member with lower face, the movable member being movable between a position spaced from a sealing position in the body when the valve is in an open position and movable to the sealing position when the valve is in a closed position, the improvement including: an annular sealing member disposed in the outer periphery of the lower face of the movable member to sealingly engage a portion of the body when the valve is in the closed position.

Abstract: A coupling for joining together opposing ends of a pressurized refrigerant flow line utilizes a quick connect feature and provides a metal-to-metal seal when connected. When disengaged, opposing ends of the fluid flow line are closed by valves, each of which includes a structure containing an axial passageway and an axially extending valve positioned therein. The valves are yieldingly urged to a closed position when disconnected. The first structure and valve are mounted in a housing having a quick connect feature for retaining the second structure and valve. When connected together, the first structure and valve is moved axially relative to the second structure and valve, while the second structure is maintained in an axially fixed position in the housing. The axially extending first valve engages the axially extending second valve moving it relative to its structure from a closed to an open position while at the same time moving relative to a cooperating sleeve from a closed to an open position.

Abstract: A fluid directional control valve has at least one working fluid control port and a pressure inlet controlled with respect thereto by a poppet valve where zero leakage sealing is achieved by provision of a poppet seat which combines a resilient seal portion with a non-deformable poppet supporting portion; has a second, axially aligned valve, which may also be a poppet assembly, for controlling fluid exhaust flow from the controlled port and has an extended plunger whereby actuation of the second valve blocks exhaust flow while unseating the pressure control poppet.

Abstract: In a preferred embodiment, in a fluid flow valve having a body and having a movable member with lower face, the movable member being movable between a position spaced from a sealing position in the body when the valve is in an open position and movable to the sealing position when the valve is in a closed position, the improvement including: an annular sealing member disposed in the outer periphery of the lower face of the movable member to sealingly engage a portion of the body when the valve is in the closed position.

Abstract: A needle valve including a deformable seal positioned between the distal end of the needle and a hard, mechanical seat between the needle and the valve housing. The deformable seal is able to seal around the movable needle but is protected from serious deformation by the hard mechanical seat that is located so as to prevent the needle from entering the deformable seat beyond a predetermined amount. Thus the deformable seal does not extrude due to the entrance of the needle and wear is reduced.

Abstract: A valve having a metal washer (5) slightly extending from the periphery of the passage of the narrowing (2) of the valve body member (1) avoiding friction of the push member (11) in said narrowing; and the formation, in the upper gasket (12) of a concave bevel (13) where the ball (14) engages, forming a contact area which increases the watertightness of the gasket. It is a feature of the drinker that the bowl (35) and the stem (36) are integral, the stem having a cruciform section reinforcing it and facilitating the fall of the water through the lower port (47) of a threaded bushing (40) screwed on a lower tubular extension (43) of the body member (1') of the valving device (1') on which extension there is also threaded a locknut (45) ensuring the position of the threaded bushing (40). A version having a single rigid gasket (8') with elimination of the washer (5) is contemplated.

Abstract: A metal diaphragm valve is disclosed, which has an improved locking mechanism capable of locking the valve in closed position. The mechanism comprises a roller that is snugly disposed in a cutout formed in the bonnet made integral with the knob which drives the diaphragm through a reciprocating plunger. The roller is made rotatable on a horizontal plane with the bonnet which is in turn turned by the knob. When the knob is turned, for an angle of 90 degrees, from the fully-opened position of the valve to the fully-closed position, the roller slips into a groove formed in a stationary member provided in the bonnet. When the roller fits into the groove, the operator can tactically feel the drop and hear a clicking sound, confirming that the valve is closed.

Abstract: A gas modulating valve for use with a gas burner is disclosed. Two variations of the valve are disclosed: the direct-discharge variation discharges a gas jet directly into the mixing tube of a gas burner, and the in-line variation meters the gas flow from the supply line to a gas manifold, which in turn terminates in one or more fixed orifices which discharge to the burner mixing tube or tubes. With respect to the moving parts, the two variations are identical. In both variations, the modulation of the gas flow is achieved by a thin moveable slide sandwiched in a planar space between two fixed valve body members, through which pass the upstream and downstream portions of a short gas discharge passageway. The slide has a hole which is positioned relative to the axis of the gas discharge passageway so as to produce a discharge orifice of variable size. The valve is sealed against leakage by face seals effected with o-rings. The valve actuator is a stepper motor which is controlled by an electronic controller.

Abstract: The present invention is directed to a valve system which upon disconnection essentially eliminates the release of liquids and vapors to the atmosphere. The invention includes a precision machined poppet and valve seat such that the leading end of the poppet and the end of the valve housing are flush when the valve is closed and such that the sides of the poppet are flush with the surface of the valve seat. Fluids and vapors are eliminated as the valve closes. The valve is not sealed until after closing. The invention is normally used with two flushly abutting valves which close sequentially for the elimination of liquids and vapors.

Abstract: A sludge pump valve for use in pumping systems which pump aggressive, abrasive, and corrosive liquids containing granular material, pumped over long distances and at high pressures, employs a pair of elastic sealing elements provided, respectively, with spherically configured convex and concave surfaces that mate along a spherical contact surface during valve closing to effect leak-free seal of the valve, the arrangement being such that valve is made more maintainence free and has a longer service life.

Abstract: A natural gas cylinder fitting and solenoid valve includes a solenoid-actuated poppet co-operating with an O-ring clamped to the floor of the valve cavity to selectively prevent or permit the passage of gas between a gas line and a natural gas cylinder. In an internally mounted embodiment, a fitting body adapted to be engaged in the neck of a cylinder isolates a low pressure region containing the electrical components of the solenoid.

Abstract: A recirculation valve for cooling a centrifugal pump. The invention comprises a valve casing having a first chamber for connection to a centrifugal pump and a second chamber for connection to a fluid outlet, a recirculation port for redirecting fluid from the first chamber to the centrifugal pump. Between the first and second chambers is a check valve means for permitting fluid flow from the first to the second chamber. Connected to the check valve means is a hollow cylindrical valve stem permitting flow from the first chamber to the second chamber. The check valve means is comprised of a circular disc which opens when the fluid pressure in the first chamber exceeds the fluid pressure in the second chamber and closes when the fluid pressure in the second chamber approaches that in the first and intermediate chambers. A two angle control surface between the check valve disc and the valve casing controls the position of the check valve relative to the flow of fluid past the valve.

Abstract: A vacuum valve that forms a tight vacuum seal is disclosed. The valve incorporates a hollow, malleable, metallic O-ring that deforms and conforms readily under pressure to seal the space between a movable valve member and a valve seat. When the valve is closed, the O-ring is compressed between opposed machined surfaces of the valve member and the valve seat, readily deforming and conforming to those surfaces, thus creating a vacuum-tight seal thereat.

Abstract: An improved gate valve comprising spaced parallel housing walls having axially aligned apertures therethrough and constituting a housing; sleeves removably coupled to the housing walls and defining an annular space therebetween; a gate plate in sliding contact with the sleeves reciprocable between open and closed positions and defining a primary seal to atmosphere between the gate plate and sleeves; packing located adjacent to the upper edges of the housing walls through which the gate plate reciprocates between open and closed positions and defining a secondary seal to atmosphere between the gate plate and the packing; and means associated with the periphery of the housing walls to retain flowing fluid within the housing walls.

Abstract: An improved pressure regulator for use in racing and other high demand environments for use with a high pressure, high output pump. The sealing plunger is designed to make a hard surface seal and also carries an "O"-ring to form a secondary seal. The primary function of the "O"-ring however, is to create a venturi in the normal ranges of operation to thus create a cushion area which prevents chattering, hydraulic hammering, pulsations, and the like in the fuel flow through the regulator.

Abstract: A seal arrangement for a metering valve wherein a cylindrical member has a groove located on a face adjacent a seat which surrounds an opening connected to an inlet port. An elastomeric member has a base which is located in the groove with a projection that extends past the face on the cylindrical member. A ring is resiliently held against the elastomeric member by a sleeve to form a first static seal between the cylindrical member, retaining ring and sleeve. A piston located in the sleeve has a flange with first and second ribs thereon separated by a recess. An input member positions the piston such that the first rib engages the projection and compresses the elastomeric member before the second rib engages the seat to form a static seal between the piston and cylindrical member to assure that fluid flow between an inlet port and an exit port terminates when the piston is in a closure position.

Abstract: An electromagnetic diaphragm-type valve has a leakage preventing convex ring and is particularly applicable to air-aided fuel injection system. The valve includes an external housing made of a magnetic-inductive material, an electromagnetic coil set installed inside the rear part of external housing, a magnetic-inductive stator fitted to the central holding site of electromagnetic coil set, and a valve stem installed in the front part of external housing. The valve stem circumference is integrated with a deflectable rubber diaphragm so as not only to enable the valve stem to move a minor distance but also to enable the valve stem to be located in a right or left position. In addition, the diaphragm isolates an air chamber from parts defining the ranges of guidance and lift of valve stem, hence the motion of valve stem is not affected by entrance of pollutants. The diaphragm is formed to seal in compresed air in the air chamber.

Abstract: A pressure release valve which includes a body having a cavity in the form of a frustum extending from a circular base and terminating in a circular opening at the top of the frustum. An annular lip extends perpendicularly from the circular opening toward the base of the body, the lip having a recessed annular shoulder. A central shaft extends axially through the circular opening in the body. A spindle head disc extends radially from the central shaft and has a circular edge seatable in the recessed annular shoulder. A top disc extends radially from the shaft, the top disc terminating in a downwardly extending flange spaced from the spindle head disc circular edge and spaced from the annular lip. Seals between the spindle head disc and the top disc provide a seal with the annular lip when the valve is in the closed position.

Abstract: A valve for use in a valve housing which forms a flow passage, an annular valve seat being provided in the passage and the seat forming an annular seal surface, the housing, the seat and the passage being concentric on a valve axis. The valve includes a valve body which reciprocates on the axis in the housing toward and away from the seat, guide means on the valve body for slidingly engaging the seat and guiding the reciprocation of the valve body on the axis, and an annular insert mounted on the valve body adjacent the seal surface and concentric with the axis. The insert comprises a rigid part and a resilient elastomeric seal part, the rigid and seal parts being bonded together. The valve body includes a radially extending portion having an outer periphery and a groove formed in the outer periphery, the insert being mounted in the groove with the seal part facing the seal surface.

Abstract: A multiple port refrigeration circuit valve uses a valve head mounted upon a threaded stem to selectively control fluid flow through the valve. While the valve housing is formed of a plurality of parts assembled by heating the construction of the valve head permits an elastomeric seal to be used in combination with metal seal surfaces, and the use of the elastomer eliminates leakage and reduces the torque required to form an effective seal.

Abstract: A reciprocating pump valve and seat having mating frustoconical seating surfaces in which a resilient sealing insert on the valve is below a rigid disc portion of the valve, with a sealing surface on the insert engageable with the seating surface of the seat radially outwardly from the portion of the seating surface of the seat engageable by the rigid disc portion of the valve.

Abstract: An improved pressure regulator for use in racing and other high demand environments for use with a high pressure, high output pump. The sealing plunger is designed to make a hard surface seal and also carries an "O"-ring to form a secondary seal. The primary function of the "O"-ring however, is to create a venturi in the normal ranges of operation to thus create a cushion area which prevents chattering, hydraulic hammering, pulsations, and the like in the fuel flow through the regulator.

Abstract: A thermostatic mixing valve is described having separate valves for hot and cold water each with a stepping motor to adjust their positions and connected to a microprocessor using a temperature sensor in a mixing chamber to read the mixed temperature and step the motors individually to adjust the valve positions as required.

Abstract: A valve element for a fluid pump comprises a rigid body and a flexible ring-shaped seal mounted on the body. The body includes an annular groove around its outer periphery in which the seal is mounted. An outer surface of the groove forms a first contact surface which engages a second contact surface defined by an inner circumference of the seal. Those contact surfaces form an angle of from 5.degree. to 10.degree. with the longitudinal axis of the valve element to resist the creation of a gap between those surfaces. The seal includes a longitudinally projecting annular finger which is hooked into a correspondingly shaped channel of the recess to secure the seal to the body. The contact surface of the seal is configured to reduce the compression imposed on the front end of the seal so as to render that front end relatively flexible and able to effectively absorb forces applied thereagainst by grit disposed in fluid being pumped.

Abstract: A valve for safeguarding the outer container of a double wall vacuum-insulated container for low boiling liquified gases against a pressure increase in the insulation space after a loss of vacuum comprises a valve housing fastened in the outer container, a valve plug and an O-ring which, as a result of deformation, act as a sealing element between the valve housing and the valve plug. The dimensions of the valve housing and seal plug causing deformation of the O-ring in the radial direction and the influence of the outside air pressure causing simulataneous deformation in the axial direction.

Abstract: A valve assembly comprises a rigid seat and a valve for opening and closing the seat. The valve comprises a rigid valve body and an elastomeric seal element mounted on the valve body. The seal element includes smoothly concave seat-engaging surface which tapers in a forward direction. An annular recess formed in a rear surface of the seal element extends to a depth at least one-third of the distance from a rear end to a front end of the concave surface to define therewith a flexible lip. The walls of the recess are oriented such that pressures present behind the valve intensify the engagement of the seal element with both the seat and valve body.

Abstract: Valve assemblies having a valve seat with a conical surface for causing an included O-ring to roll upon and wedge against the conical surface for closing the port when a spherical valve member is forced against the O-ring.

Abstract: A double seat valve includes a housing with a pair of valve disks independently movable within the housing between a closed position and an open position. Further, the valve disks can also be moved as a unit. A hollow leakage space is located between the valve disks. Leakage can be conveyed from the space to the exterior of the housing. Each valve disk has a separate valve seat and a cylindrically shaped wall surface extends between the valve seats and defines the radially outer boundary of the leakage space. A seal mounted in the first valve disk contacts the first valve seat in the closed position and moves in sealing contact with the cylindrically shaped wall surface as the first valve disk moves from the closed position toward the open position so that leakage losses from the valve are avoided.

Abstract: An improved valve seal is provided which utilizes a c-shaped secondary seal. The c-shaped seal is positioned between the valve disc and the valve seat. A retainer locates the c-shaped seal with respect to the disc, retains the seal against the disc and provides a pre-load on the seal as required.

Abstract: A fluid valve with improved valve trim for reliable fluid shut off in high pressure applications. The improved valve trim includes a flexible metal seat with a lip portion which flexes outwardly upon sealing contact with a valve plug seating surface. A deformable seal mounted in the seat is prevented from substantial outward movement by a rigid metal seal retainer and is squeezed outwardly around the plug seating surface as the seat lip portion flexes outwardly.

Abstract: A valve assembly for use in a sprinkler head comprising a valve seat having a generally frusto-conical surface configuration and an annular rib, a flanged valve member in sealing engagement with said annular rib and having a depending, radially inwardly spaced surface which in cooperation with said annular rib and surface configuration forms a partially enclosed space in which a resilient O-ring is captively held in compressive engagement between the valve seat and valve member.

Abstract: A valve, particularly useful in a fire extinguisher, which utilizes a stem movable in a passageway having a head connected to the stem. The head includes a relatively hard member possessing a hard outer surface which fits snugly within the passageway. The head further includes a deformable portion adjacent the relatively hard surface of the relatively hard member. The relatively hard surface of the relatively hard portion contacts and scrapes the wall portion prior to sealing which is effected between the deformable portion and the wall of the passageway.

Abstract: An automatic air pressure relief and check valve assembly which may be used in combination with a swimming pool filter or separation tank. The valve assembly includes a normally open lower valve which is responsive to the tank's being full of water for closing the lower valve, and a normally closed upper valve which is responsive to air being expelled from the tank through the normally open lower valve for opening the upper valve during times when water is filling the tank. The upper valve may be selectively opened when air is required to enter the tank so that water may be drained from the tank. Preferred embodiments of the upper and lower valves include valve seats having conical surfaces and respective valve members which cause an included O-ring to roll upon and wedge against its conical seat for reliably closing each valve.

Abstract: Disclosed is a mud pump valve which includes a seat ring adapted for insertion in a mud pump. The seat ring includes a frusto-conical seating surface and an annular seal ring groove about its outer periphery. A seal ring is positioned in and bonded to the seal ring groove. The seal ring has a frusto-conical sealing surface having an angle of taper greater than that of the seating surface of the seat ring. A closure disc is reciprocatingly mounted with respect to the seat ring and the closure disc includes a frusto-conical sealing surface having an angle of taper substantially the same as the angle of taper of the seating surface of the seat ring.

Abstract: A valve joint, in particular, a measuring valve joint for fluid systems with high working pressures, comprises a connector bushing under line pressure having a spring-loaded and mechanically operable check valve in a bore. A cylindrical valve body in the bore presses its packing shoulder against a sealing ring consisting of an elastomeric material in the closed state of the valve. A sealing liner and the valve body form a sealable flow channel arranged in the connector bushing. Further seals are arranged downstream and/or upstream from the sealing ring. Upon the opening of the valve body the further seals terminate their sealing function only after the lifting of the sealing ring from the packing shoulder and preferably in a delayed manner.

Abstract: High-pressure, micrometering valves requiring low-actuating torque are combined in a lightweight, portable pressure calibration console, housed in a common valve block. A manual pressure valve and a manual vent valve connect compressed gas from an internal storage cylinder to pressure measuring gages or transducers to be calibrated. Automatically actuated isolation valves connect and disconnect a vernier balancing cylinder assembly, permitting fine manual adjustment of calibration pressures as high as 10,000 psi. Positive shutoff combined with low-torque, fingertip control and non-jamming closure are provided by the frictionally-engaged valve components.

Abstract: A globe valve (10) is disclosed which reduces the pressure drop across a soft seal (38) as it moves into and out of engagement with a seal surface (24) on the valve body (12) to reduce the wear effect of the pressure drop, particularly in control of gas flow with maximum pressures of approximately 6000 psi. A hard seal (28) is resiliently mounted on the valve stem (20) to engage the valve seal surface of the valve body prior to engagement of the soft seal to reduce the pressure drop across the soft seal.

Abstract: A soft rubber seal member is molded in the cavity in the face of the valve core. During the molding process air can escape through the slots or gates in the annular ring in the face of the valve core. When rubber starts coming out the gate, the gates are closed off and the rubber hardens in the gates. The valve is used in combination with a valve housing provided with an entry orifice having a diverging exit section leading to a flat annular surface against which the flat central portion of the soft rubber seal will seat when the valve is closed. This obtains a large seating area and ensures uniform valve opening pressure.

Abstract: A sealing system for a valve disposed downhole in a subterranean well and subject to a high-temperature and high-pressure environment, comprises an annular valve seat defining a primary annular metallic seating surface surrounded by a groove within which is mounted a nonresilient, nonmetallic sealing element which is spring urged to project axially beyond the end of the primary sealing surface. The valve head is provided by a primary metallic sealing surface which, as the valve head moves toward engagement with the valve seat first engages the nonresilient, nonmetallic sealing element and deflects same axially and concurrently expands it radially outwardly so that the nonmetallic, nonresilient sealing element ends up engaging a cylindrical surface surrounding the primary sealing surface formed on the valve head.

Abstract: A glass precision valve for use in liquid measuring instruments, the valve comprising a valve body having a conically sharpened head slidably accommodated in a bulged portion, which includes glass tubes at opposite ends, a valve seat provided by the inside wall of the bulged portion, the surface of the valve seat allowing the conically sharpened head of the valve body to be slidable in a liquid-tight manner, and the valve body including a ring-shaped groove around its axis, the ring-shaped groove being filled with an elastic material.

Abstract: The disclosure is related to a high pressure fluid control valve including a valve seat made from a resilient, deformable material and a main valve plug which is matable with the resilient, deformable valve seat. A selectively, axially displacable valve stem is associated with the valve plug whereby a contact load placed upon the valve plug by the valve stem will cause the valve plug to be become imbedded within the deformable material comprising the valve seat when the valve is closed and thereby conform the deformable seat precisely to the contour and configuration of those portions of the valve plug which mate with the valve seat. In this manner, a precise zero-leakage mating is obtained each and every time the plug is mated with the seat. In accordance with the invention, an auxiliary throttle plug is associated with the main valve plug and is arranged to mate with a second, metal valve seat which is arranged in an area removed from the resilient, deformable valve seat.

Abstract: A stem tip seal for a shut-off valve including a valve member adapted for selective movement axially toward and away from an associated valve seat. A generally cylindrical sleeve is carried by the valve member and has an end defining an outer annular seal surface adapted for cooperative sealing engagement with the seat. Mounted centrally within the sleeve for limited axial movement is a rigid cylindrical body that defines a first inner annular seal surface adapted for engagement with the seat at a location radially inwardly of the outer annular seal surface. Formed between the sleeve and the rigid body is an annular chamber which opens axially inwardly from a narrow slot located between the first inner annular seal surface and the outer annular seal surface. A mass of resilient packing material substantially fills the chamber and extends axially outwardly of the slot to define a second inner annular seal surface.